The present invention relates to lensless image projectors, and in particular to art projectors used by artists to enlarge sketches and reference photos.
Most image projectors require a darkened room for their use. Those projectors include movie projectors, slide projectors (for transparencies), opaque projectors (for photos), and LCD projectors (for computer images). Overhead projectors work well in partially lighted rooms by employing very large projection lenses.
Many painters use art projectors to enlarge sketches or photos onto their work surfaces (canvas, watercolor paper, etc.). Those art projectors, also called opaque projectors, require a darkened room in order to achieve a clear and sufficiently contrasted projected image. The requirement of a darkened room severely inconveniences the use of art projectors. When working during the daytime, one must either shade all the room windows with opaque material, or have access to a room without windows. If they cannot darken a room during the day, then they must enlarge their images after dusk.
Another limiting characteristic of art projectors is that the larger the desired magnification of the original, the larger must be the distance from the projector to the projection surface. So even if the artist has access to a small room without windows, they will not be able to achieve large image magnifications in such a small room.
A further limiting characteristic of current art projectors is that they operate with high voltage (household voltage) and utilize high-powered bulbs making them unsafe for use by kids under about twelve years of age without supervision.
Since the present invention employs a projection system based on the principle of the shadowgraph, it seems appropriate to bring forth some examples of prior art related to shadowgraph projectors.
A shadowgraph is essentially a shadow of an object obstructing light that emanates from a point light source. The shadow will be a sharp image of the object""s contour. The object obstructing the light may be a dark line drawn on a transparent sheet. Such a dark line will also produce a sharp shadow of itself when illuminated by a point source of light. In reality it is not possible to create a perfect point light source, but a close approximation may be had from a miniature lamp such as a flashlight lamp having a very small filament.
Examples of projection devices utilizing the shadowgraph principle are U.S. Pat. Nos. 1,972,123, 1,992,776, 2,048,365, and 3,401,596.
What is common to all the above-mentioned inventions is that they all require a darkened environment in order to see a clear projected image. And, as has been mentioned above, the requirement of a darkened environment is a limitation of most projection devices seen today.
Accordingly, it is an object of the present invention to provide an image enlargement apparatus that does not require a darkened environment for its use.
Another object of the invention is to provide an image enlargement apparatus that does not require an increasingly larger space for increasingly larger magnifications.
It is a further object of the present invention to provide a battery operated, low power projection apparatus that is independent of electrical wall outlets and is quite safe for kids to use.
These and other objects are achieved by the present invention that provides a lensless, battery operated image projection apparatus that is enclosed within a collapsible, darkened enclosure.
The projection system consists of a point light source in the form of a flashlight lamp, a transparency platform located under the lamp, and the projection surface located under the platform. The artist""s working surface is placed on the projection surface and, in effect, becomes the projection screen.
To enlarge an image such as a photo, first a transparency is made by tracing the original image onto a clear sheet of plastic. The transparency is placed onto the transparency platform. When the lamp is turned on in a darkened environment, an enlarged shadow of the transparency is seen on the projection surface below. The enlarged shadow is then traced onto the artist""s working surface.
The projection system and projection surface described above are enclosed inside a pyramid-shaped tent that provides a darkened enclosure for projection in a lighted environment.
A more complete understanding of the present invention and other objects, aspects and advantages thereof will be gained from a consideration of the following description of the preferred embodiments read in conjunction with the accompanying drawings provided.